Men who eat lots of walnuts can protect themselves against prostate cancer. This is suggested by an animal study that biologists at the University of Texas published in 2013 in Cancer Investigation. Walnuts contain substances that sabotage the spread and growth of prostate cancer tumours.

Study
The researchers gave mice subcutaneous injections of human prostate cancer cells [LNCaP]. Some of the mice were given standard feed [Control diet]; others were given feed that contained 11 percent walnuts [Walnut diet].

The researchers ensured that both diets contained the same amount of calories, fibre, fats, carbohydrates and proteins.

Results

In the mice that had not been given walnuts, the researchers found tumours in 44 percent of the animals in the end. In the walnut group only 18.7 percent developed tumours.

The tumours in the walnut group were smaller than those in the other group.

The photo below shows on the left a typical prostate cancer tumour that the researchers found in the walnut diet group, and on the right the biggest tumour in the mice that did not get walnuts.

The researchers found that the mice that had been given walnuts had fewer F2-isoprostanes in their livers. F2-isoprostanes are released when free radicals go to work on cell membranes. That would suggest that walnuts have an anti-oxidant effect.

Mechanism
"Walnuts have a number of ingredients that could account for their ability to suppress prostate tumor growth," the Americans write. "Most notably, walnuts contain high levels of omega-3 fatty acids."

"The elevated intake of long-chain 20c eicosapentaenoic acid (EPA) and 22c docosahexaenoic acid (DHA) fats, in particular, slows cancer growth. The walnut diet used in the current study, however, contained essentially no EPA or DHA. Hardman and Ion [ Nutr Cancer 2008;60:666-74.] have documented, however, that the mouse liver has the capability of elongating and desaturating alpha-linolenic acid (ALA) to EPA and DHA, probably in small amounts."

"Other walnut ingredients that, theoretically at least, could explain the inhibitory effect of the walnut diet on LNCaP prostate cancer cells inoculated into nude mice include phytosterols, gamma-tocopherol, carotenoids, polyphenolics, ellagic acid and its derivatives, and melatonin. The bulk of these phytochemicals function as antioxidants, which generally are beneficial in terms of cancer suppression."

"The seemingly most likely explanation for the finding that a walnut-enriched diet forestalled the growth of human prostate cancer cells growing in immune-compromised mice is that the inhibitory effect was a consequence of the combined actions of several phytochemicals in this nut which have been shown individually to inhibit experimental prostate cancer."

Sponsor
The study was not financed by a nut-growers' association, but by the American Institute for Cancer Research.